2002 Yamaha YFM660 Grizzly factory service and repair manual, Page 136Get this manual
CHECKING THE BATTERY
Batteries generate explosive hydrogen gasAlways follow these preventive measures: Charge batteries in well-ventilated areaKeep batteries away from fire, sparks or open flames (e.g welding equipment, lighted cigarettes, etc DO NOT SMOKE when charging or handling batteriesKEEP BATTERIES AND ELECTROLYTE OUT OF REACH OF CHILDREN1.Remove: Seat Battery holding bracket Battery lead cover Refer to "SEAT, CARRIERS, FENDERS AND FUEL TANK"
2.Disconnect: Battery leads